Low-cost sedimentation deposition of boron nanoparticle films for thermal neutron detection applications

The stagnating supply of ³He, the essential material used in gas proportional counters for neutron detection, has recently motivated research activity in solid boron thin-film deposition. The isotope ¹⁰B can be used to replace ³He as the neutron reactive material that produces charged reactants to enable detection. In our research, we developed a process for depositing boron films via nanoparticle sedimentation out of a suspension solution. The simple process, in comparison to conventional vacuum deposition techniques, is expected to reduce processing cost and maximize material utilization during fabrication of large-area neutron detection systems. The work being reported here details the process for producing the boron film by the sedimentation method and analyzes the physical properties of the resulting films. Also, the neutron conversion efficiency of the film was evaluated, and the performance results compared favorably to a sputtered ¹⁰B₄C conversion film employed in commercial large-area neutron straw detector systems, suggesting its potential to become an appealing option for use in large-area neutron detectors after further optimization. We also investigated the effect of boron nanoparticle films’ thickness on the neutron conversion efficiency. The optimal film thickness tends to be slightly larger than what is expected for pure B solid film, due to porosity in the film.